diff --git a/src/kiri/print.js b/src/kiri/print.js
index 0205f059..80bf8327 100644
--- a/src/kiri/print.js
+++ b/src/kiri/print.js
@@ -1272,6 +1272,7 @@
                 if (typeof v === 'number') {
                     eva.push(`let ${k} = ${v};`);
                 } else {
+                    if (v === undefined) v = '';
                     eva.push(`let ${k} = "${v.replace(/\"/g,"\\\"")}";`);
                 }
             }